The present invention relates to a double-acting cylinder-piston unit for generating the feed motion of a saw blade in the direction into a workpiece and for generating the cutting pressure in a mechanical frame saw whose saw blade is clamped in obliquely of a saw frame guide.
Such a cylinder-piston unit is connected pivotably on the one hand with the machine frame and on the other with the housing part which contains the saw frame guide and the saw frame drive and which is pivotably mounted on the machine frame. Furthermore, a first cylinder chamber of the unit, loaded by the hydraulic medium generating the cutting pressure, is connected with a reservoir for the hydraulic pressure medium through an adjustable cutting pressure valve in the form of a spring-loaded throttle valve which opens when the set cutting pressure is exceeded, and through a non-return valve which closes when the cutting pressure is reached in the first chamber. The second cylinder chamber of the unit, loaded by the weight of the articulated housing part, is in communication with the reservoir through an adjustable throttle valve and a suction valve in the form of a non-return valve.
Such cylinder-piston units are used in mechanical frame saws such as are disclosed for example in German Pat. Nos. 1,502,987 and 2,525,154. In these machines, the housing part containing the saw frame guide and the saw frame drive is mounted pivotably, with its rear end in relation to the saw blade, on the machine frame and supported ahead of this mounting, in the direction toward the saw blade, against the cylinder-piston unit, the latter being primarily articulated with the piston rod to the pivotable housing part, while it is connected, via its cylinder, with the fixed machine frame.
A cylinder-piston unit of the initially mentioned kind is disclosed especially in German Pat. No. 2,525,154. Here the cylinder jacket is surrounded by the oil reservoir and the feed motion valve, and the two non-return valves are arranged one behind the other axially in the hollow-bored piston rod, with the piston and the cylinder wall adjoining the latter at the end. The cutting pressure valve is arranged on the other side of the cylinder, in the cylinder head which is located there, from where pressure medium can flow back into the oil reservoir on the jacket.
This above-outlined known structure is distinguished by compactness. However, it necessitates a relatively expensive type of construction with many individual parts, which correspondingly influences the costs for constructing the known cylinder-piston unit. This relates specifically also to the circumstance that in the known case the piston rod which functions as a bearing or loaded component must be bore out and correspondingly dimensioned.